I would highly recommend doing the Discover Lisbon tour when first arriving in the city! Paulo provides a vast overview of the history of the city, which really brings the monuments and buildings to life. There is so much context that I would not have gotten had I only wandered around on my own. I was able to take lots of great pictures of the main attractions but also the streets of the different neighborhoods (Alfama was my favorite). This tour is offered at a great value, and I will recommend to anyone who visits!